Re: [Phys-l] definition of gravity

[John Mallinckrodt <ajm@csupomona.edu>]

Thanks for biting.  My guess is that some folks would claim that the gravitational field "at that position" is 3/4 g toward the ground.  The observed acceleration of freely falling objects in a frame attached to that position however is 31/36 g toward the ground.  In my world that means that the gravitational field in that frame is 31/36 g.  Note that I didn't say and you certainly shouldn't assume that the Earths are (somehow!?) *held* with their centers 3 Earth radii apart.

John Mallinckrodt
Cal Poly Pomona

On Nov 10, 2011, at 9:38 AM, brian whatcott wrote:

> On 11/8/2011 3:27 PM, John Mallinckrodt wrote: /snip/
> > Here's a question that might be instructive to work out: Suppose you 
> > have two non-rotating Earth's with a center to center distance of 3 
> > Earth radii. What gravitational field (in terms of g, the 
> > gravitational field on an isolated non-rotating Earth) would be 
> > determined by a person standing at the point on the surface of one of 
> > the Earths that is closest to the other Earth? Is it the same as the 
> > acceleration that person observes for an object dropped to the ground? 
> > John Mallinckrodt Cal Poly Pomona
> .
> .
> .
> I'm always up for instruction - and supposing there are factors I'm 
> ignoring:
>  I imagine the acceleration would be about 0.75g
>
> What would it really be?
>
> Brian W
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